This invention relates to compositions of matter which are useful as addition polymerization catalysts, to a method for preparing these catalysts and to a method of using these catalysts. More particularly, this invention relates to catalyst compositions useful as olefin polymerization catalysts and to a method for polymerizing olefin monomers using the same.
In EP-A 416,815, published Mar. 13, 1991, there are disclosed certain constrained geometry complexes comprising a constrain inducing delocalized n-bonded moiety and metals of Groups 4-10 of the Periodic Table of the Elements. Such compositions formed catalysts in the presence of activating cocatalysts such as alkylalumoxanes, aluminum alkyls, aluminum halides, aluminum alkylhalides, Lewis acids, ammonium salts, noninterfering oxidizing agents and mixtures of the foregoing.
In U.S. Pat. No. 5,026,798 and U.S. Pat. No. 5,055,438 Group IV B metallocene compounds having a heteroatom ligand in combination with an alumoxane were disclosed as suitable olefin polymerization catalysts.
In EP-A418,044, published Mar. 20, 1991 (equivalent to U.S. Ser. No. 07/758,654 now U.S. Pat. No. 5,132,380) and in U.S. Ser. No. 07/758,660 now abandoned certain cationic derivatives of the foregoing constrained geometry catalysts that are highly useful as olefin polymerization catalysts are disclosed and claimed. In U.S. Ser. No. 720,041, filed Jun. 24, 1991, now abandoned certain borane derivatives of the foregoing constrained geometry catalysts are disclosed and a method for their preparation taught and claimed.
For the teachings contained therein, the aforementioned pending United States Patent applications, issued United States Patents and published European Patent Applications are herein incorporated in their entirety by reference thereto.
Although previously known cationic catalysts, especially the cationic catalysts disclosed in the foregoing applications and publications, have excellent activity, they are extremely sensitive to catalyst poisons, such as polar impurities, that may be contained in a polymerization mixture. Because of this fact, catalyst lifetimes have been limited and molecular weights of the resulting polymers have been reduced.
It is previously known in the art to utilize adjuvants such as trialkylboron and trialkylaluminum compounds to remove catalyst poisons from biscyclopentadienyl containing olefin polymerization catalysts. Disadvantageously however, such adjuvants have proven to be ineffective in combating the inhibition of cationic catalysts, especially cationic, constrained geometry catalysts, and when used in the polymerization of olefin monomers especially, actually may interfere with the desired catalytic process.
In J. Am. Chem. Soc., 113, 8570-8571 (1991), it has furthermore been reported that the use of alumoxanes in combination with biscyclopentadienyl containing cationic catalysts results in detrimental interference with the catalyst for propylene polymerizations.
It would be desirable if there were provided improved, cationic catalyst compositions having constrained geometry that are resistant to the effects of catalyst poisons.
In particular, it would be desirable if there were provided improved, cationic, constrained geometry, catalyst compositions having extended catalyst lifetimes and improved polymerization efficiencies.